The present invention relates to fluid moving mechanisms and more specifically to a rotary fluid mechanism possessing a very high displaced volume to size ratio i.e., the displaced fluid per revolution is large compared to the volume of the mechanism which moves this fluid. The object of a high displacement-to-size ratio fluid mechanism is to obtain less mechanism friction in order to reduce either the power consumption to drive this mechanism as a fluid pump, or to reduce the fluid energy required to operate the device as a fluid motor or meter.
The common prior art positive displacement fluid mechanisms possess relatively higher internal friction or resistance to flow and larger size and weight for equivalent displacement and higher noise levels as represented by the vane, piston, and gear types of fluid mechanisms.
For example, rotary vane fluid mechanisms most commonly consist of a rotor with sliding vanes mounted eccentrically in a circular or elliptical chamber. To keep leakage to an acceptable value the vanes must provide a contact seal to a cam ring introducing friction forces and wear proportional to the number of vanes, the vane sealing surface and size of the cam ring. Typically vane mechanisms exhibit high vane friction and leakage, low efficiency, and require a substantial pressure differential to operate which produces a lateral force on the rotor that is transmitted to the associated shaft and bearings. The vane mechanism has a poor displacement-to-size ratio as compared to the present invention. The aforementioned properties are true for both the fixed and variable-displacement vane type mechanism.
The piston type mechanism can be classified by the basic relationship between the piston and the piston barrel. The axial-piston version, have pistons that lay approximately along the axis of the barrel, whereas, in the radial-piston mechanisms, the pistons radiate outward from the barrels. The axial piston requires the complexity of an angled cam (or wobble) plate or the use of the bentaxis principle and usually require some type of check valve.
The radial-piston version requires a rotating cam that runs through the center of the mechanism imparting reciprocating motion to the pistons. Check valve complexity is also usually required in this configuration.
These basic piston mechanisms and many variations all require piston seals to reduce leakage, have a relatively high resistance to mechanical motion and have higher pressure drops when compared with the present invention. Energy loss due to the normal cyclic motion is also encountered with piston mechanisms and many cylinders are required for smooth operation. The major disadvantages of the piston mechanisms are the large size, complexity, and higher friction required for performance equal to that of the present invention.
Gear type mechanisms have numerous configurations including gear-on-gear, three-gear, gear-within gear, and screw gear mechanisms and in general, are fixed displacement devices having high bearing loads, high friction and require heavier bearings, housings and shafts as compared to the present invention. Leakage of fluid that can be forced past internal seals between inlet and outlet ports is also very high for the gear type mechanisms. To reduce leakage at the gear interface, high contact forces and high precision are required resulting in increased size, weight and basic resistance of the mechanism. These mechanisms usually exhibit a low displacement-to-size ratio and are generally low pressure devices, have low mechanical efficiency and are noisy in operation.
Another version somewhat similar in characteristics to the gear mechanism is the lobed-rotor mechanism. This mechanism consists of two rotating elements that revolve in opposite directions in a chamber. The rotors usually do not touch and, therefore, have a very high fluid leakage.
Other prior art in rotary mechanisms similar to the invention do not offer the advantage of simple construction, novel porting between rotating chambers and a high displacement-to-size ratio with low mechanical resistance. In general all the prior art in positive displacement mechanisms require larger mechanisms with greater resistance to mechanical motion for the same fluid displacement per shaft revolution.